1. Field of the Invention
The present invention relates to the synthesis of azines in reaction zones having a reduced content in CO.sub.2.
2. Description of the Prior Art
The synthesis of hydrazine from ammonia and aqueous hydrogen peroxide is described in Ullmann's Encyclopedia of Industrial Chemistry, vol. A 13, pages 182-183 (1989).
In a first stage, an azine is formed according to the reaction: ##STR1##
This reaction is carried out in the presence of a catalyst or mixture of catalysts. Such catalyst is employed in the form of a working solution. Upon completion of the reaction, the azine is separated from the working solution.
The working solution is regenerated and then recycled to the first stage. In a second stage, the azine is hydrolyzed to hydrazine and the ketone recovered is also recycled to the first stage: ##STR2##
The above process is described, for example, in U.S. Pat. Nos. 3,972,878, 3,972,876, 3,869,541, 3,948,902, 3,956,282, 3,943,152, 4,725,421, 4,093,656, 4,724,133 and in EP-399,866.
In the first stage, the introduction of the reactants NH.sub.3 and H.sub.2 O.sub.2 is carried out.
It has now been found that the presence of CO.sub.2 should be avoided to as great an extent as possible during the azine synthesis reaction. For example, when conducting the synthesis of azines by reacting methyl ethyl ketone, NH.sub.3 and aqueous hydrogen peroxide in the presence of a working catalyst solution comprising an aqueous solution of acetamide, sodium acetate and disodium phosphate, it was noted that the loss of aqueous hydrogen peroxide by decomposition increased in direct proportion to the CO.sub.2 concentration in the reaction mixture, namely, the totality of the working solution plus reactants.